Manufacture of soft luster filaments



Patented July 27, 1937 UNITED STATES MANUFACTURE OF SOFT LUSTER FILA- NTS Hugo Hofmann, Elizabethton, Tenn, assignor to American Bemberg Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application November 22, 1933,

Serial No. 699,198

11 Claims.

In the early days of .rayon manufacture the demand was entirely for yarns with a high degree of luster. However, when it was found that the highly'lustrous rayon filaments too clearly signified its origin-an artificial fibre-a demand arose for rayon which would more closely resemble natural silk. Many methods have meanwhile been developed to produce so-called dull luster filaments, either by inclusion of solid phases, such as oxides andpigments, or of liquid phases, for example, vegetable and mineral oils, etc., into artificial silk spinning solutions; or by etching and/or coating the unfinished, as well as the finished, filaments or threads with suitable chemicals. Mechanical delustering methods have also been employed, e. g., abrading, etc.

One object of my present invention is to produce a dull luster filament or thread of artificial silk without the aid of any pigments or oils.

Another object of my invention is to produce a dull luster filament by first effecting a thin coating on the outside of an artificial silk filament by means of suitable chemicals in the spinning bath, for example, the wash-water, and subsequently rupturing the coating in statu nascendi".

A third object of this invention is to add such compounds to the Wash-wate'rin' funnel apparatuswhich form water-soluble complex copper salts, e. g., ammines, by chemical reaction, for example, with the cuprammonium solution.

Other objects of my invention will be apparent from the following disclosure and the appended claims.

From the discussion, supra, in which the known methods of producing dull luster filaments,yarn, etc:, were discussed, it Will be readily apparent that I have produced adull luster yarn without employing any of the known methods. By extruding afilament, simultaneously coating it by chemical andyor physical reaction without employing: any foreign chemical compound, and then, in statu-nascendi, rupturing this coating, I have evolved an entirely new and novel procedure for the-productionof dull luster yarn, filaments, thread, and the like.

I am well aware that electrolytes of high and lowconcentrations have, heretofore, been used in the wash water of spinning funnels to produce lustrous filaments; but I believe myself to bathe first inventor to suggest the addition of electrolytes of a definite concentration and chemical nature to realizethe production of dull luster filaments. When cellulose linters are dissolved in cuprammonium solution (Schweitzers reagent) and drawn in funnels, in the presence of water, with or without additional chemicals, a skin forms on the outside of the cellulose filament while its core is still in a very plastic state.

By stretching, the filament is elongated and. its

diameter is reduced before total coagulation occurs. The ultimate result is a lustrous filament. When large amounts of electrolytes are present in the wash-water, a spontaneous coagulation takes place on the surface of the filament and the formation of a continuous filament by the stretch-spinning process becomes impossible. However, by experimentation, I have found that certain electrolytes which cause, by coagulation, the formation of a thin, brittle surface skin on the filament in statu nascendi are suitable for producing dull luster filaments, provided that the aforementioned surface skin is ruptured by stretching at the moment it is being formed.

These electrolytes may either be added to the spinning solution itself or to the wash-water.

My invention, essentially, lies in'the fact that I cause ammoniumsalts or acids to bepresent in the wash-water in amounts sufiicient to cause the formation of complex cuprammonium salts without altering the bath to such an' extent that it is nolonger alkaline in reaction. That is, when ammonium salts are added, the ammonia acts to' form a water-soluble copper tetrammine salt. When acids are added tothe water, they should be in stoichiometric proportions with respect to the free .ammonia present so that a neutral ammonium salt of theacid is formed. This prevents the formation of an acid spinning water, and consequently the water is still alkaline inreaction.

This is essential to my invention:

1. The presence of salts, as noted, to react to form a water soluble copper tetrammine salt;

and

2. When acids are added, the amount added must be so controlled that the spinning water in the funnel remains alkaline in reaction.

My-invention gives altogether unexpected results. This is evidencedby the fact that hitherto ammonium sulphate has been termed the enemy of stretch spinning, and efforts have always been made to prevent the presence of this salt. I have found, however, that the presence of a small amount of this salt, within a certain range 'ofconcentration, results in the production of a low luster yarn without the use of any of the formerly known delustering processes.

When'from 0.9 to 1.6 grams of ammonium sulphate, containing 2.46 to 4.37 'per cent of reactive NH4, for example, are added to one liter of washwater, or cuprammonium-cellulose solution, according to my theory, a water-soluble copper tetrammine sulphate is formed on the outside of the filament, thus causing the formation of a surface coating which, in turn, produces a dull luster cellulose filament, on being ruptured by stretching. The reactions involved are probably the following:

Microphotographs and optical analysis of the filament indicate that this dulling is caused by the formation of an amorphous layer of cellulose which may be called an amorphous cellulose, although its chemical characteristics have not been clearly determined. The inner core of the filament, being produced under tension, exhibits the characteristics of a more clearly marked orientation. The outside of the filament is, because of its coating of amorphous cellulose, considerably rougher than that of ordinary cuprammonium filaments. It is the presence of this coating of cellulose on the filament which allows it to reflect light rays in such a manner that the surface of the filament appears dull, as distinguished from shiny.

It is to be noted that my process is not limited to the production of dull luster filaments from cuprammonium spinning solutions. It may be used to produce such filaments from any other cellulosic spinning solution such as viscose, cellulose ethers, cellulose esters, casein solutions,

' etc. Viscose filaments, for example, may be produced in a bath, with a low degree of stretch in the conventional manner, quickly run through a second bath of cuprammonium solution to soften their surface, and a surface coating produced in a third bath, and this coating ruptured by stretching. The first bath must be of such a low concentration that complete coagulation of the filament of viscose does not occur, and there must not be freeacid present to such an extent that the other baths are rendered acidic in reaction. Viscose or casein solutions may also be directly spun under tension in funnels like cuprammonium solutions to produce dull filaments.

In the manufacture of low luster filaments from cuprammonium solutions, I have found it advisable to use a roller rather than a rod in the apparatus employed. Such an arrangement is covered specifically in a copending application. Also, the filaments may be collected in spinning pots.

sulphate to be formed. This complex compound acts to form a coating of cellulose on the outer surface of the filament. Just as it is being formed, the stretching action being applied by the roller acts to rupture this coating in a multitude of places. The stretching is such that the diameter of the filament is reduced to from 1/250th to l/300th of its original size, as extruded. As the filament emerges from the spinnerette it comprises a core of orientated cellulose surrounded by a coating of amorphous cellulose.

As a second example, a cellulose solution is prepared as indicated in Example 1, above, and, in the spinning water, has ammonium sulphate present at a concentration of 5 grams per litre. The filaments, as spun, are not reeled into skeins, as in the case in Example 1, but are collected in spinning pots. I have found that this concentration of salt gives a very desirable dull luster when spinning pots or buckets are employed. Possibly because of the rate of spinning in the centrifugal method, as differentiated from the rate in the ordinary skein method, plus the production of a twisted yarn by the centrifuge process, a concentration of salt as high as 5 grams per litre may be employed. The specific application of my invention with respect to the centrifugal process will, however, form the subjectmatter of a copending application.

The present application is prepared for the purpose of protecting my generic invention as applied to the formation of dull luster artificial filaments. An explanation of the manner of producing both cuprammonium and viscose dull luster filaments by this process has been given.

It is not necessary for me to limit myself to ammonium salts such as the sulphate, tartrate, oxalate or acetate, for example, but, as pointed out supra, I may employ acids. As an example,

sulphuric, tartaric, acetic, or some other similar I acid may be present in the spinning water in such a concentration, that together with the free ammonia of the cuprammonium solution,--

an ammonia salt of the desired concentration is formed. This salt immediately reacts in the manner set forth above, to form the complex copper salt and produce the desired coating, to be ruptured in statu nasoendi. By statu nascendi as used throughout this specification, I mean at the very moment when the coating is formed.

This invention is broadly and fundamentally novel in its concept, so I do not wish to be limited in the disclosure otherwise than by the scope of the appended claims.

What I claim is:

1. The process of producing dull luster filaments from cellulosic spinning solutions comprising extruding a filament simultaneously producing a thin coating of a cellulosio material on the filament, and rupturing said coating, in statu nascendi, by stretching.

2. The process of producing dull luster filaments from cellulosic spinning solutions comprising extruding a filament simultaneously producing by coagulation a thin coating of a cellulosic material on the filament, and rupturing said coating, in statu nascendi, by stretching.

3. The process of producing'dull luster filaments from cuprammonium cellulose solution comprising extruding a filament forming a thin coating of a cellulosic material on the filament and rupturing said coating, in statu nascendi, by stretching.

4. The process of producing dull luster filaments from cuprammonium cellulose solution comprising extruding a filament forming by coagulation a thin coating of an amorphous cellulose on the filament and rupturing said coating, in statu nascendi, 'by stretching.

5. The process of producing dull luster filaments from a viscose solution comprising extruding a filament forming a thin coating of a eellulosic material on the filament and rupturing said coating, in statu nascendi, by stretching.

6. The process of producing dull luster filaments from a cuprammonium solution comprising drawing said solution off in a funnel apparatus under tension, said funnel containing wash Water having about 0.9 to 1.6 gr./litre of ammonium sulphate dissolved therein. v

7. A dull luster cellulosic filament comprising an inner core of cellulose and a coating consisting of a ruptured cellulosic material.

8. A dull luster cuprammonium filament comprising an inner core of cellulose and a coating consisting of a ruptured cellulosic material.

9. A dull luster viscose filament comprising an inner core of cellulose and an outer shell of amorphous cellulose.

10. In a process for manufacturing dull luster filaments from cuprammonium solutions, the steps of extruding a cuprammonium solution into a funnel containing wash-water to which from 0.9 to 1.6 gr./litre of ammonium sulphate has been added, and then immediately stretching the filaments.

11. In a process for manufacturing dull luster filaments from cuprammonium solutions, the steps of extruding a cuprammonium solution into a funnel containing wash-water to which suflicient sulphuric acid has been added to form, on dissociation, by reaction with the free NH: present from the cuprammonium solution, from 0.9 to 1.6 gr./litre of ammonium sulphate, and stretching the filaments.

HUGO HOFMANN. 

